Closed-Loop Boost PFC Circuit for Current-Source LED Lighting
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Solution Overview
Problem
Existing airfield lighting systems using current source input face challenges in achieving good power factor and harmonic control, especially with higher power LED lights, requiring efficient power factor correction (PFC) to meet standards and reduce power consumption, distortion, and component stress.
Innovation Solution
A boost-based PFC topology with closed-loop control that uses a current transformer, diode bridge rectifier, ceramic capacitor, boost converter, and DC-DC converter, along with output voltage and current sensing, to achieve sinusoidal input voltage and efficient LED operation without bulky capacitors or AC side sensing, utilizing analog control for dynamic response and reliable start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional AC voltage source is used, then the system can operate with standard rectification, but power factor is poor and harmonic distortion is high
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors the input current and adjusts the boost converter duty cycle to maintain unity power factor. The feedback mechanism compares the actual input current with the desired sinusoidal waveform and dynamically adjusts the switching parameters to minimize harmonic distortion and maximize power factor, achieving both improvements simultaneously.
Solution Approach 2:
The patent transforms the input current waveform parameters through the boost converter, changing it from a distorted non-sinusoidal waveform to a clean sinusoidal waveform. By dynamically adjusting the converter operating parameters (duty cycle, switching frequency) based on load conditions, the system maintains optimal power factor and minimizes harmonics across varying operating points.
2Illumination intensity
If higher power LED lights are used, then illumination intensity increases, but power factor correction becomes more difficult and component stress increases
Solution Approach 1:
The patent employs a dynamic control system that adapts to varying power levels and load conditions. The closed-loop controller continuously adjusts the boost converter parameters based on real-time feedback, enabling the system to handle higher power LED loads while maintaining component stresses within safe operating limits. This dynamic adaptation prevents overload conditions and extends component life.
3Loss of energy
If AC voltage sensing is implemented, then power factor control can be achieved, but hardware cost and circuit complexity increase
Solution Approach 1:
The patent extracts the voltage sensing function from the traditional AC voltage sensing approach and replaces it with a current-only sensing methodology. By using only current sensors and deriving all control information from input current measurements, the system eliminates the need for separate voltage sensing circuits, reducing hardware cost and complexity while maintaining effective power factor control through the closed-loop system.
4Loss of energy
If standard PFC circuits are used, then power factor correction is achieved, but start-up reliability is poor and large capacitors are required
Solution Approach 1:
The patent implements a preliminary start-up sequence where the boost converter is pre-charged through a dedicated start-up circuit before normal operation begins. This preliminary action ensures that the capacitor is adequately charged and the control system is ready before full power operation commences, improving start-up reliability and eliminating the need for excessively large capacitors that would be required for direct-on-line starting.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides efficient power factor correction with low harmonic distortion, reduced component stress, and smooth LED start-up, ensuring compliance with power standards and improved reliability and efficiency.
Implementation Method 1
a current transformer configured to step down a current from a current source
Implementation Method 2
a diode bridge rectifier connected to the current transformer
Implementation Method 3
a boost converter having a start-up diode and connected to the capacitor
Data Source
AI summary
Boost-based power factor correction with closed-loop control is described herein. Some embodiments include a current-source fed power factor correction circuit, comprising a current transformer configured to step down a current from a current source, a diode bridge rectifier connected to the current transformer, a capacitor connected to an output of the diode bridge rectifier, a boost converter having a start-up diode and connected to the capacitor, a direct current (DC)-DC converter connected to an output of the boost converter and configured to regulate an operation of a light-emitting diode (LED), a voltage sensor configured to determine output voltage, and a current sensor configured to determine a current associated with the diode bridge rectifier.